Boom stop



May 15, 1945. .T. w. THOMAS BOOM STOP Filed Aug. 9, 1943 2 Sheets-Sheet l INVENTOR. THUITIFIS Lu- THUITIFIS y 15, 1945. T. w. THOMAS 2,376,019

BOOM STOP Filed Aug. 9, 1943 2 Sheets-Sheet 2 INVENTOR. THEHTIFIS LU- THEHTIFIS STATE PATENT OFFICE e BOOM s'ror- Thomas twm Thomas, San Rafael, Calif. H i i I' 1 Application August 9, 194a, No. 497,957 lClaims. (01. 212-39) I This inventiom relates to improvements in power releasing devices, and-hasparticular reference to a device tor releasing the: power asapplied to a crane boom.

over backwards, endangering the life of the operator, distorting the boom and causing considerable damage; I

I have, therefore; devised a mechanismwhich may be attached to the ordinary crane in alignment with the boom, whereby when the same The; principal objectof this invention is to 5 t provide means for; automatically stopping crane does reach a predetermined elevation, a contact been at a predetermined point its upward will be made which will'release the dnvmg mechtmvek H e I U v anism, thus arresting any further movement of A further object is to provide means. whereby the boom Whlch W111 v t damage thereto, the boom be lowered, itr-vhase been and thus save costly repair bills as well as loss stopped,

i e of the use of the crane during the repair period. A further object isto providea device of this Refelrmg i the drawmgs detall, Pamcuj character which may be applied to'any standard the numem1.5 deslgnates the lowel form of c'ra-ne boomwithout materially altering 15 en of a P Y P d s at 6. its construction-or operation;- r i h l g mechamsl'r} has been Omltted, 1n p I e der to simplify the drawings.

A further ob ect is to produce a device wh ch 1 I h is econ mical' to "manufacture. and one which will shown power umt Whlcb dnves t s a shaft 8 through a master clutch 9, which may not'become deranged m be manually operated by a lever II or through a qthertfibjects a fifnfifi fi 333E332? the use of a booster cylinder and piston as shown urmg e course 0 e I I e In the accflmpanying drawings forming ap rt it gi g gg i '3 compressed an i this e a n and m which like numerals The parts thus far described are common to are employed designate Iike'parts throughgut all crane arrangements whether they be gasor 4 line driven or electrically driven. I I

F 1S d e re lllustretwn of i My invention comprises the employment of a Vice as same WW1? be apphed to prank pair of cylinders, one of which is the air-release P m mechanism cylinder Hi, and the other a resetting cylinder u sldeeelevatlon of b mg ll. The air-release cylinder i6 is mounted upon n release cylmderand Shown partly 311cm the cab of the crane or in any other convenient sectfllon- I place, whereby the head His in alignment with Fig; III 1s. a side elevation of the foot pedal and a pad I 9 mounted on t boom 5' e t Cylinder and shflwn Partly in cross The head I8 is mounted on the end of a valve t1on,, y 1 rod-2|, which enters the cylinder l6 and, has a Cranes amusedior' F P handLImg valve 22 formed upon its opposite end. This heafvy loads ({ompnse a Power .mechamsm valve in turn normally seats on a seat 23 formed which in turn drives; gears through :a master in a division wall 24 within the cylinder l6,1which clutch. The gears in turn actuate drums, over n forms'ehambers A and A Spring 2 w ich e p which cables aroused for e mally' holds this valvein its seated position. v e e o and handlmgload- 4 A pipe 21- conducts air from the tank 14' tothe 'Cranes are usually mountedupon portablecar chamber A f t e cylinder i5. s ria s, whe eby the c ane as a whole may be -A pipe 26 conneots'the chamber B of the cylm v f m p ce to lace intransportingtm inder IS with the chamber C of the cylinder 11.. load. j H j t e c This cylinder likewise'has a division wall, as It often" occurs that an ope tor w n l shown at Z9,'which is provided with a valve seat to disconnect the boom-liftin m n m While 3|, against which a valve '32 is adapted to seat. the crane'is being propelled over its course of valve 32' is carried on avalve rod 33 passtravel, the result being that when the boom ing through the end of the cylinder I1 and termoves upwardly to a predetermined angle, it will minating in a head 34, against which the bifurengage a, fixed stop onthe supporting structure cated end 36 of a foot pedal 31 contacts, the and further movement ofthe boom will be arpedal being pivoted as at 38. rested. If the hoisting mechanism continues to' A spring 39 positioned within the chamber D exert a pull on the boom, the boom will be bent, normally maintains this valve 32 out of contact with its seat 3|.

pipe 2'! through the chamber A into the chamber B through the pipe 28 into the chamber C, past the open valve 32 into the pipe 4| and into the booster cylinder I2, with the result that the booster cylinder will actuate the master clutch, releasing the power from the gear and cable mechanism, thus instantly stopping any further upward travel of the boom.

As this air is under very high pressure, its travel from the static state in the cylinder A to the booster cylinder [2 is very rapid, so that an almost instantaneous stoppage of the hoisting of the boom occurs.

The booster I2 is provided with a constantly open bleeder 43; therefore, in order to reset the mechanism so that the boom may be lowered and the clutch released, the operator steps upon the foot pedal '31, which moves the bifurcated end against the head 34, which pulls the valve'32 to a closed position, thus preventing any further passage of air from the tank l4 to the booster.

The bleeder now serves to release pressure in the booster cylinder an enables the operator to manually throw the master clutch to engage the power.

As soon as the boom starts to travel away from the air release cylinder the spring 26 functions to close the valve 22 against its seat 23, after which the operator may remove his foot from the foot pedal, and the mechanism will again be in normal working condition. It will thus be seen that by applying this simple mechanism to any ordinary crane, or similar mechanism having a movable member, it is possible to prevent damage to the movable member, thus eliminating expensive repairs, loss of the use of the crane during the repair period and providing protection to the operator against physical injury. It is to be understood that the form of my invention herewith shown and described is to be taken as a preferred example of the same and that various changes relative to the material, size, shape and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. In a fluid pressure-actuated limit stop for the control clutch of a, hoist boom, a cylinder having a partition therein dividing the same into two separate chambers with one of said chambers in constant communication with a source of compressed air, a valve in said partition having a tensioned rod extending through one end of the cylinder and adapted to be operated for inserting said valve, a second cylinder having a partition therein forming two chambers and having a valve seat, with a tensioned normally inserted valve therein, means forming communication between one end of the second cylinder and the chamber of the first cylinder normally out of communication with the source of compressed air, a control clutch, clutch actuating mechanism, means forming communication between the second cylinder and the clutch actuating mechanism and manually operated means for closing the valve in the second cylinder for closing communication between the sec-0nd cylinder and the clutch actuating mechanism.

2. In a fluid pressure actuated limit stop for the control clutch of a hoist boom, a source of power and a master clutch, a pair of cylinders in communication with each other, a source of compressed air in communication with one cylinder and means forming communication between the other cylinder and the master clutch, a control valve in the cylinder'communicating with the source of compressed air and normally shutting off'communication between the two cylinders and adapted to be operated by a boom to form communication between the two cylinders whereby compressed air may flow through the second cylinder for the operation of the operating means for the master clutch and means for shutting off communication between the second cylinder and the master clutch.

3. In a fluid pressure actuated limit stop for the control clutch of a hoist boom, 2. source of power and a master clutch, a pair of cylinders in communication with each other, a source of compressed air in communication with one cylinder and means forming communication between the other cylinder and the master clutch, a control valve in the cylinder communicating with the source of compressed air and normally shutting off communication between the tw cylinders and adapted to be operated by a boom to form communication between the two cylinders whereby compressed air may flow through the second cylinder for the operation of the operating means for the master clutch and manually operated means for shutting ofif communication between the second'cylinder and the master clutch.

4. In a fluid pressure actuated limit stop for the control clutch of a hoist boom, a source of power and a master clutch, a pair of cylinders in communication with each other, a source of compressed air in communication with one cylinder and means forming communication between the other cylinder and the master clutch, a control valve in the cylinder communicating with the source of compressed air and normally shutting off communication between the two cylinders and adapted to be operated by a boom to form communication between the two cylinders whereby 

